Puzzles are simple when it comes to rules. Match colors, draw a line etc. That means it doesn't require a lot of though or concentration like "deeper" games with stories and such. Puzzles also don't require a lot of time so if you need to quit rapidly you can do so. I see more and more...

I honestly believe that puzzle games are the gateway for other genres. Most people start playing puzzles games. Let's think back in time to the original puzzles, Tetris and cetipede. Just playing these games made players hungry for more. I remember playing these games for hours. (Still do). Puzzles...